He'll first appear in season four of the spin-off show and with Fear still assumed to be a few years behind The Walking Dead chronologically, it must mean that Morgan will die in season eight and we'll see an earlier version of him in Fear, right?

Well, not quite. Even though Morgan has been in The Walking Dead from the very first episode, he has gone missing for long stretches and there's definitely scope to fill in his backstory – but that's not the only way Fear can go.

We've broken down the likely ways that Morgan could fit into the new show.

1. The "father-son bonding time" theory

After he decides not to go to Atlanta with Rick in the first season, all we know is that Morgan and his son Duane live on in King County, with Morgan struggling to finally kill his undead wife. This eventually leads to her biting and killing Duane, after which Morgan starts to lose his sanity. But before all that, there's a chance he might run into characters from Fear while hanging out with Duane.

There are two issues with this, though. One is location: it's not exactly walking distance from King County, Georgia, to Texas, where season four of Fear is presumed to be set. Just because Fear is shooting in Texas, however, that doesn't mean it'll be set there.

The bigger issue is that Adrian Kali Turner is now too old to play Duane in this time period, meaning they'd have to recast Duane, and it would seem a bit odd to have the original Morgan with a new Duane.

2. The "Crazy Morgan" theory

When The Walking Dead meets up with Morgan again in season three's 'Clear', he has lost his marbles and has a shoot-out with Rick, Carl and Michonne in King County. After they manage to subdue him, Morgan explains what happened to Duane and, seeing Rick is gearing up for war, he decides not to join them as he doesn't want to see anyone else die.

So Rick leaves Morgan for the second time and we have another time period where Morgan could come across some of the Fear gang. Again there's the issue of location, but thanks to season six's stand-out episode 'Here's Not Here', we know that Morgan leaves King County after he accidentally burns his home down.

The problem is that we also already know Morgan is 'saved' when Eastman finds him in the woods, taking it on himself to teach Morgan the ways of non-violence.

This means that the period for this theory has to be after Duane's death (or after the events of 'Clear', perhaps) but before Morgan meets Eastman – and, really, that doesn't lend itself to an extended storyline on Fear. Meaning the whole crossover would be a bit pointless.

3. The "tracking Rick" theory

After he is 'cured' by Eastman, we know that Morgan starts to head towards Terminus, but we only got brief snippets of his journey during the season five premiere and the mid-season finale. It took until the season five finale for Morgan to meet up with Daryl and Aaron, going back with them to Alexandria where he meets up with Rick just as he executes Pete Anderson. Awkward timing.

This means there's another part of Morgan's off-screen Walking Dead journey where he can come into contact with Fear characters, but the biggest sticking point with this is that it would be a bit weird for Morgan to have shown up at Alexandria and not go, 'Oh, hey, I met this other group of survivors on the road…'

Or maybe it'll turn out that Morgan has been a double agent this whole time. (Almost definitely not.)

4. The "time jump" theory

We've left our strongest theory till last as it makes the most sense. What if Morgan survives season eight, decides he's had enough of Rick and heads off on his own adventure? For this to work, Fear would have to have a significant time jump following the devastating events of season three's finale, allowing the characters to meet up with Morgan.

A popular fan theory suggests that Fear is actually the origin story of the Whisperers, classic Walking Dead villains in the comics, with Madison (Kim Dickens) being the group's leader Alpha. Some fans even think that the helicopter Rick spotted in season eight's fifth episode actually belonged to the Fear lot, solving any logic issues regarding distances between the two groups.

And if they are the Whisperers, it could make sense for Morgan to be the source of their information about another group of survivors.

Even if the Fear group has come in peace and aren't the Whisperers, that doesn't rule out their meeting up with Morgan and uniting with the TWD group through him. It certainly fits with Walking Dead showrunner Scott M Gimple's saying Morgan "has a lot of story left" and his arc in season eight "positioned him for the story on Fear".

Just showing flashbacks of Morgan in Fear doesn't exactly fit with those quotes.

The Walking Dead airs on AMC in the US and on FOX and NOW TV in the UK, while Fear the Walking Dead airs on AMC in the US and BT TV in the UK.